Wireless communication systems have been developed to allow transmission of information signals between an originating location and a destination location. Both analog (first generation) and digital (second generation) systems have been developed to transmit information signals over communication channels linking the source and destination locations. Digital methods tend to afford several advantages over analog systems. For example, improved immunity to channel noise and interference, increased capacity, and encryption for secure communications are advantages of digital systems over analog systems.
While first generation systems were primarily directed to voice communication, second generation systems support both voice and data applications. Numerous techniques are known in second-generation systems for handling data transmissions which have different transmission requirements—data transmission being typically of relatively short duration, as compared to voice transmission, and usually not requiring continuous access to the communication channel. Several modulation/coding arrangements have been developed, such as frequency division multiple access (FDMA), time division multiple access (TDMA) and code division multiple access (CDMA), to increase the number of users that can access a wireless network. CDMA systems are more immune to multiple path distortion and co-channel interference than FDMA and TDMA systems and reduce the burden of frequency/channel planning that is common with FDMA and TDMA systems.
In a CDMA system, a unique binary code sequence is assigned to each active user within a cell to uniquely identify the user and spread the user's signal over a larger bandwidth. Multiplied by the assigned code, the user's signal is spread over the entire channel bandwidth, which is wider than the user signal bandwidth. The ratio of the system channel bandwidth to the user's bandwidth is the “spreading gain” of the system. The capacity of the CDMA system is proportional to the “spreading gain” for a given signal-to-interference (S/I) level. After reception of the transmitted signal, the signal of each user is separated, or de-spread, from the other users' signal by using a correlator keyed to the code sequence of the desired signal.
First-generation analog and second-generation digital systems were designed to support voice communication with limited data communication capabilities. Third-generation wireless systems, using wide-band channel management technologies such as CDMA, are expected to effectively handle a large variety of services, such as voice, video, data and imaging. Among the features which will be supported by third-generation systems is the transmission of high-speed data between a mobile terminal and a land-line network. As is known, high-speed data communications is often characterized by a short transmission “burst” at a high data transmission rate, followed by some longer period of little or no transmission activity from the data source. To accommodate the burst nature of such high-speed data services in third-generation systems, it is necessary for the communications system to assign a large bandwidth segment (corresponding to the high data rate) from time to time for the duration of the data burst. With the ability of the third generation systems to handle such bursty high-speed data transmission, throughput and delay for users can be advantageously improved. However, because of the large amount of instantaneous bandwidth required for transmission of a burst of high-speed data, the management of such bursts, and particularly the allocation of power and system resources thereto, must be handled with care to avoid unwarranted interference with other services using the same frequency allocation.
In allocating power and system resources, the designer of a high speed burst transmission network must consider the effect of the duration assigned to the burst on system resources. By transmitting data packets in bursts—i.e., individual data packets packaged together and transmitted as a single data burst, system resources are conserved as only one transmitter configuration setup is necessary for each data burst. However, bursts that are long in duration, thereby accommodating a large number of data packets in each burst, may result in an unnecessary expenditure of system resources as the burst may continue even after all the data scheduled for transmission within the burst has been transmitted. On the other hand, burst duration times which are relatively short may also cause unnecessary expenditure of system resources as the number of burst transmissions necessary to completely transmit the data message is increased and, correspondingly, the overhead and time delay for transmission of the data are increased.